1. Transparent Glass Prism
L
I
G
H
T

2. Prism and refraction
n
ectio
l d ir
tia
A Ini
N
δm N
Emer
ging ray
ra y
id ent Prism
Inc
A is the angle of prism
N is normal on the surface of prism
δm is the deviation of emerging ray from initial direction

3. Dispersion of white light of sun by prism
Spectrum
A
Red 6600 Å
Orange 6100 Å
ig ht Yellow 5800 Å
wh
it el prism Green 5500 Å
Blue 4700 Å
Indigo 4400 Å
Violet 4100 Å
wavelength λ of the center of color band in angstroms
If a shaft of light entering a prism is sufficiently small such
that the coloured edges meet, a spectrum results

4. An experiment to observe spectrum
white light Spectrum

5. Deviation by prism
Angle of dispersion θ
A δm
Θ δR
δV θ = δV - δR
t
e ligh Dispersive power ω
Whit
θ
ω=
δm
δR ⇒ deviation for red
δV - δR
δV ⇒ deviation for violet ω=
δm
δm ⇒ mean deviation or deviation
for yellow

6. Deviation by prism
Angle of dispersion θ
A δm
Θ δR
δV θ = δV - δR
t
e ligh Dispersive power ω
Whit
θ
ω=
δm
δR ⇒ deviation for red
δV - δR
δV ⇒ deviation for violet ω=
δm
δm ⇒ mean deviation or deviation
for yellow